Linux and UNIX Man Pages

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the correspond-
ing Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

NAME

mkfifo - make FIFO special files

SYNOPSIS

mkfifo [-m mode] file...

DESCRIPTION

The mkfifo utility shall create the FIFO special files specified by the operands, in the order specified.
For each file operand, the mkfifo utility shall perform actions equivalent to the mkfifo() function defined in the System Interfaces volume
of IEEE Std 1003.1-2001, called with the following arguments:
1. The file operand is used as the path argument.
2. The value of the bitwise-inclusive OR of S_IRUSR, S_IWUSR, S_IRGRP, S_IWGRP, S_IROTH, and S_IWOTH is used as the mode argument. (If the
-m option is specified, the value of the mkfifo() mode argument is unspecified, but the FIFO shall at no time have permissions less
restrictive than the -m mode option-argument.)

OPTIONS

The mkfifo utility shall conform to the Base Definitions volume of IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
The following option shall be supported:
-m mode
Set the file permission bits of the newly-created FIFO to the specified mode value. The mode option-argument shall be the same as
the mode operand defined for the chmod utility. In the symbolic_mode strings, the op characters '+' and '-' shall be interpreted
relative to an assumed initial mode of a= rw.

OPERANDS

The following operand shall be supported:
file A pathname of the FIFO special file to be created.

STDIN

Not used.

INPUT FILES

None.

ENVIRONMENT VARIABLES

The following environment variables shall affect the execution of mkfifo:
LANG Provide a default value for the internationalization variables that are unset or null. (See the Base Definitions volume of
IEEE Std 1003.1-2001, Section 8.2, Internationalization Variables for the precedence of internationalization variables used to
determine the values of locale categories.)
LC_ALL If set to a non-empty string value, override the values of all the other internationalization variables.
LC_CTYPE
Determine the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to
multi-byte characters in arguments).
LC_MESSAGES
Determine the locale that should be used to affect the format and contents of diagnostic messages written to standard error.
NLSPATH
Determine the location of message catalogs for the processing of LC_MESSAGES .

ASYNCHRONOUS EVENTS

Default.

STDOUT

Not used.

STDERR

The standard error shall be used only for diagnostic messages.

OUTPUT FILES

None.

EXTENDED DESCRIPTION

None.

EXIT STATUS

The following exit values shall be returned:
0 All the specified FIFO special files were created successfully.
>0 An error occurred.

CONSEQUENCES OF ERRORS

Default.
The following sections are informative.

APPLICATION USAGE

None.

EXAMPLES

None.

RATIONALE

This utility was added to permit shell applications to create FIFO special files.
The -m option was added to control the file mode, for consistency with the similar functionality provided by the mkdir utility.
Early proposals included a -p option similar to the mkdir -p option that created intermediate directories leading up to the FIFO specified
by the final component. This was removed because it is not commonly needed and is not common practice with similar utilities.
The functionality of mkfifo is described substantially through a reference to the mkfifo() function in the System Interfaces volume of
IEEE Std 1003.1-2001. For example, by default, the mode of the FIFO file is affected by the file mode creation mask in accordance with the
specified behavior of the mkfifo() function. In this way, there is less duplication of effort required for describing details of the file
creation.

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE
and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained
online at http://www.opengroup.org/unix/online.html .